Docker 与 K8S学习笔记（十六）—— kubectl命令行工具使用
kubectl作为客户端命令行工具，可以让用户通过命令行方式对kubernetes集群进行操作，这一篇将对其使用进行说明。
一、语法结构
kubectl [command] [TYPE] [NAME] [flags]
command：指对一种资源索要执行的操作，如create、get、describe、delete。
TYPE：资源类型，资源类型不区分大小写， 可以指定单数、复数或缩写形式如：pod、deployment、service。下表是目前支持的资源类型（通过kubectl api-resources即可获取）：
$ sudo kubectl api-resources NAME SHORTNAMES APIVERSION NAMESPACED KIND bindings v1 true Binding componentstatuses cs v1 false ComponentStatus configmaps cm v1 true ConfigMap endpoints ep v1 true Endpoints events ev v1 true Event limitranges limits v1 true LimitRange namespaces ns v1 false Namespace nodes no v1 false Node persistentvolumeclaims pvc v1 true PersistentVolumeClaim persistentvolumes pv v1 false PersistentVolume pods po v1 true Pod podtemplates v1 true PodTemplate replicationcontrollers rc v1 true ReplicationController resourcequotas quota v1 true ResourceQuota secrets v1 true Secret serviceaccounts sa v1 true ServiceAccount services svc v1 true Service mutatingwebhookconfigurations admissionregistration.k8s.io/v1 false MutatingWebhookConfiguration validatingwebhookconfigurations admissionregistration.k8s.io/v1 false ValidatingWebhookConfiguration customresourcedefinitions crd,crds apiextensions.k8s.io/v1 false CustomResourceDefinition apiservices apiregistration.k8s.io/v1 false APIService controllerrevisions apps/v1 true ControllerRevision daemonsets ds apps/v1 true DaemonSet deployments deploy apps/v1 true Deployment replicasets rs apps/v1 true ReplicaSet statefulsets sts apps/v1 true StatefulSet tokenreviews authentication.k8s.io/v1 false TokenReview localsubjectaccessreviews authorization.k8s.io/v1 true LocalSubjectAccessReview selfsubjectaccessreviews authorization.k8s.io/v1 false SelfSubjectAccessReview selfsubjectrulesreviews authorization.k8s.io/v1 false SelfSubjectRulesReview subjectaccessreviews authorization.k8s.io/v1 false SubjectAccessReview horizontalpodautoscalers hpa autoscaling/v1 true HorizontalPodAutoscaler cronjobs cj batch/v1beta1 true CronJob jobs batch/v1 true Job certificatesigningrequests csr certificates.k8s.io/v1 false CertificateSigningRequest leases coordination.k8s.io/v1 true Lease endpointslices discovery.k8s.io/v1beta1 true EndpointSlice events ev events.k8s.io/v1 true Event ingresses ing extensions/v1beta1 true Ingress flowschemas flowcontrol.apiserver.k8s.io/v1beta1 false FlowSchema prioritylevelconfigurations flowcontrol.apiserver.k8s.io/v1beta1 false PriorityLevelConfiguration ingressclasses networking.k8s.io/v1 false IngressClass ingresses ing networking.k8s.io/v1 true Ingress networkpolicies netpol networking.k8s.io/v1 true NetworkPolicy runtimeclasses node.k8s.io/v1 false RuntimeClass poddisruptionbudgets pdb policy/v1beta1 true PodDisruptionBudget podsecuritypolicies psp policy/v1beta1 false PodSecurityPolicy clusterrolebindings rbac.authorization.k8s.io/v1 false ClusterRoleBinding clusterroles rbac.authorization.k8s.io/v1 false ClusterRole rolebindings rbac.authorization.k8s.io/v1 true RoleBinding roles rbac.authorization.k8s.io/v1 true Role priorityclasses pc scheduling.k8s.io/v1 false PriorityClass csidrivers storage.k8s.io/v1 false CSIDriver csinodes storage.k8s.io/v1 false CSINode storageclasses sc storage.k8s.io/v1 false StorageClass volumeattachments storage.k8s.io/v1 false VolumeAttachment
NAME：资源名称，区分大小写如果省略名称，则显示所有资源的详细信息，这里支持两种资源指定方式：
-
按类型和名称指定资源，例如：kubectl get pod nginx
-
使用文件指定资源，例如：kubectl get -f ./nginx_pod.yaml
flags：指定可选的参数。例如，可以使用 -s 或 -server 参数指定 Kubernetes API 服务器的地址和端口。
二、操作示例
1、创建资源对象
我们根据yaml配置文件创建Nginx的Deployment，yaml文件内容下：
apiVersion: apps/v1 kind: Deployment metadata: name: nginx-deployment labels: app: nginx spec: replicas: 3 selector: matchLabels: app: nginx template: metadata: labels: app: nginx spec: containers: - name: nginx image: nginx:latest ports: - containerPort: 80
创建资源：
$ sudo kubectl create -f nginx_deployment.yaml deployment.apps/nginx-deployment created
2、查看资源对象：
$ sudo kubectl get pods NAME READY STATUS RESTARTS AGE nginx-deployment-585449566-28gxs 1/1 Running 0 31s nginx-deployment-585449566-f7vnt 1/1 Running 0 31s nginx-deployment-585449566-jpc2z 1/1 Running 0 31s $ sudo kubectl get deployments NAME READY UP-TO-DATE AVAILABLE AGE nginx-deployment 3/3 3 3 66s
3、查看资源对象描述信息
$ sudo kubectl describe pod nginx-deployment-585449566-28gxs Name: nginx-deployment-585449566-28gxs Namespace: default Priority: 0 Node: ayato/172.16.194.135 Start Time: Thu, 23 Dec 2021 02:12:57 +0000 Labels: app=nginx pod-template-hash=585449566 Annotations: <none> Status: Running IP: 172.17.0.7 IPs: IP: 172.17.0.7 Controlled By: ReplicaSet/nginx-deployment-585449566 Containers: nginx: Container ID: docker://49099a8d907ff1c28f557de3c3ee84d90113c33578caddfd70d3bd0e72da67d5 Image: nginx:latest Image ID: docker-pullable://nginx@sha256:366e9f1ddebdb844044c2fafd13b75271a9f620819370f8971220c2b330a9254 Port: 80/TCP Host Port: 0/TCP State: Running Started: Thu, 23 Dec 2021 02:13:15 +0000 Ready: True Restart Count: 0 Environment: <none> Mounts: /var/run/secrets/kubernetes.io/serviceaccount from default-token-pcr2h (ro) Conditions: Type Status Initialized True Ready True ContainersReady True PodScheduled True Volumes: default-token-pcr2h: Type: Secret (a volume populated by a Secret) SecretName: default-token-pcr2h Optional: false QoS Class: BestEffort Node-Selectors: <none> Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s node.kubernetes.io/unreachable:NoExecute op=Exists for 300s Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 98s default-scheduler Successfully assigned default/nginx-deployment-585449566-28gxs to ayato Normal Pulling 97s kubelet Pulling image "nginx:latest" Normal Pulled 82s kubelet Successfully pulled image "nginx:latest" in 15.804248355s Normal Created 81s kubelet Created container nginx Normal Started 81s kubelet Started container nginx
4、查看容器内日志
$ sudo kubectl logs nginx-deployment-585449566-28gxs /docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration /docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/ /docker-entrypoint.sh: Launching /docker-entrypoint.d/10-listen-on-ipv6-by-default.sh 10-listen-on-ipv6-by-default.sh: info: Getting the checksum of /etc/nginx/conf.d/default.conf 10-listen-on-ipv6-by-default.sh: info: Enabled listen on IPv6 in /etc/nginx/conf.d/default.conf /docker-entrypoint.sh: Launching /docker-entrypoint.d/20-envsubst-on-templates.sh /docker-entrypoint.sh: Launching /docker-entrypoint.d/30-tune-worker-processes.sh /docker-entrypoint.sh: Configuration complete; ready for start up 2021/12/23 02:13:15 [notice] 1#1: using the "epoll" event method 2021/12/23 02:13:15 [notice] 1#1: nginx/1.21.4 2021/12/23 02:13:15 [notice] 1#1: built by gcc 10.2.1 20210110 (Debian 10.2.1-6) 2021/12/23 02:13:15 [notice] 1#1: OS: Linux 4.15.0-163-generic 2021/12/23 02:13:15 [notice] 1#1: getrlimit(RLIMIT_NOFILE): 1048576:1048576 2021/12/23 02:13:15 [notice] 1#1: start worker processes 2021/12/23 02:13:15 [notice] 1#1: start worker process 31 2021/12/23 02:13:15 [notice] 1#1: start worker process 32
这里也可以加上-f参数即：sudo kubectl logs -f nginx-deployment-585449566-28gxs，其效果和tail -f一样能够持续跟踪查看日志。
5、登陆到指定pod的容器中，需要指定pod和容器名，容器名在刚才的yaml中有定义，也可以通过describe命令查看
$ sudo kubectl exec -it nginx-deployment-585449566-28gxs -c nginx /bin/bash kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead. root@nginx-deployment-585449566-28gxs:/#
PS：在进行操作时，大家可能会遇到集群拉取镜像失败问题导致pod起不来，这个需要在启动minikube时指定国内的镜像仓库：
minikube start --vm-driver=none --registry-mirror=https://registry.docker-cn.com
